Bioidentical hormones are completely safe. The FDA is not aware of any credible scientific evidence to support claims made regarding the safety of compounded bioidentical hormones. The Director of the FDA’s Office of Women’s Health states, "They are not safer just because they are natural.” The FDA points out that bioidentical hormones have not been studied in large clinical safety trials, so we don’t know if they are safe or not. Intuitively, we know that estrogen feeds breast cancer. Buyers beware.